Erlangen 2026 – scientific programme

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T: Fachverband Teilchenphysik

T 10: Axions/ALPS I

T 10.2: Talk

Monday, March 16, 2026, 16:30–16:45, KH 01.013

Search for axion-like particles with gluon couplings in B→ Ka, a→π⁺π⁻π⁰ at the Belle II experiment — •Karlina Kröhnert, Priyanka Cheema, and Torben Ferber — Institute of Experimental Particle Physics, Karlsruhe Institute of Technology, Karlsruhe, Germany

Axion-like particles (ALPs) appear in different theoretical extensions to the Standard Model. This analysis targets ALPs within a mass range of 400 MeV to 1 GeV and with gluon couplings produced in hadronic B decays. A particularly interesting decay mode is a → π⁺ π⁻ π⁰ since, for ALP-gluon couplings within the reach of the Belle II sensitivity, it produces a long-lived ALP a.

Although large parts of the parameter space have been explored by beam dump experiments and former prompt searches by BaBar and Belle, the displaced signature of the ALP offers a promising possibility to significantly extend existing ALP-gluon coupling limits.

In this analysis we search for an ALP in a→π⁺π⁻π⁰ using B→ Ka decays at Belle II. We highlight how the displaced signature offers the possibility of significantly suppressing the background, but leads to unique challenges regarding the π⁰ reconstruction from displaced vertices.

This talk will show the status of this search and present sensitivity estimates based on the current Belle II data set.

Keywords: Axion Like Particle; Dark Sector; Belle II; Physics Beyond the Standard Model